Nitrous oxide (inspired 76 percent; 45 minutes) did not alter the concentration or turnover rate of acetylcholine in any of the brain areas studied. Pentobarbital (65 mg/kg; i.p.) reduced the turnover rate and increased the levels of acetylcholine in cortex, hippocampus and diencephalon but not in striatum. The local anesthetics, lidocaine and cocaine (100 mg/kg; s.c.; 39 minutes), did not change the steady-state concentrations of acetylcholine. Lidocaine decreased the acetylcholine turnover rate in the cerebral cortex; whereas cocaine, which causes hypermotility, increased the acetylcholine turnover rate in the cerebral cortex and the diencephalon but not in the striatum or the hippocampus.